Hand held electronic devices such as personal digital assistants (PDA's) and cell phones have employed hinged covers or lids to provide physical protection for a keypad and/or a touch sensitive liquid crystal display (LCD).
U.S. Pat. No. 5,956,656 discloses a PDA with a hinged cover movable from a closed position to an open position where it remains, inclined slightly to a vertical axis, under the influence of gravity.
As hand held electronic devices, particularly cell phones, have become more compact, it has become commonplace to utilize a foldable lid or flip cover embodying a microphone to maintain an effective spacing between the loudspeaker and microphone of a cell phone to align with the ear and mouth of a user.
For convenience, it is considered desirable that a cell phone be operated in a one handed mode rather than with two hands as with some earlier cell phones which relied upon a stiff or frictional hinge mechanism to maintain the flip in a closed or open position.
U.S. Pat. No. 5,689,824 and U.S. Pat. No. 6,363,243 each describe a cell phone having a flip cover biased to a normally open position by a spring mechanism but otherwise able to be latched into a closed position by a mechanical latching mechanism.
A magnetic latch mechanism having a magnetic attraction force greater than the biasing force of a flip cover opening spring is disclosed in each of U.S. Pat. Nos. 5,706,332 and 6,151,486. The former patent relies upon a spring loaded magnet carrier to move one magnet in a cell phone body out of alignment with a fixed magnet in a cell phone flip until the magnetic closing force is exceeded by the spring biased opening force. The latter patent relies upon a selectively actuated magnetic field generator to reduce the magnetic attraction force between aligned magnets in the cell phone body and the flip cover.
U.S. Pat. No. 5,274,882 describes a cell phone having an axially biased flip hinge mechanism wherein the cell phone flip cover is located in an open or closed position by a socket and spigot engagement mechanism. Opening and closing of the flip cover in this type of cell phone requires a two handed operation.
Another type of flip cover requiring a two handed operation to open and close the flip cover is described in U.S. Pat. No. 6,374,089. This patent describes a damper mechanism in the form of an electric motor associated with the pivotal movement of the flip to provide a sense of resistance in rotation of the flip cover.
While generally satisfactory for their respective intended purposes, such prior art flip cover mechanisms either require a two handed operation or otherwise require expensive and relatively fragile latching mechanisms with protruding latch actuators enabling accidental opening of a flip cover under normal handling conditions. Accordingly, there is a need for a simple, inexpensive and robust latching mechanism for hand held electronic devices, which mechanism may be operated in a one handed operation.